ENHANCING THE ELECTRONIC LIBRARY SYSTEM
THROUGH THE INTEGRATION OF HETEROGENEOUSDATA SOURCESHIRONOBU GOTODA, KEIZO OYAMA, and JUN ADACHINational Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan
Email: {gotoda, oyama, adachi}@nii.ac.jp

ABSTRACTNACSIS-ELS is an electronic library service of Japanese academic journals provided by National
Institute of Informatics (NII). In this paper, we will describe how the functionality of NACSIS-ELS hasbeen enhanced since its initial startup in 1997. NII has been compiling and providing other databases suchas CiNii, REO, and Webcat Plus afterward, and the metadata of all these sources are being integrated intoa unified system. We will illustrate the details of this system design, and explain the technologies
supporting the integration. The issues for further development are also mentioned, in particular, thecooperation with other services.

INTRODUCTION
National Institute of Informatics (NII) is an inter-university research institute in Japan founded in April
2000. NII takes over the development and operation of the infrastructure for disseminating the scholarly
information, which National Center for Science Information Systems (NACSIS) had been concerned withfor a long time in cooperation with the universities and national institutions in Japan. The Electronic
Library Service, called NACSIS-ELS, is an outcome of such activities, from which researchers canretrieve via the Internet the photographic reproductions of academic journals and magazines as well as
their bibliographic information [1-3].
As of June 2005, more than 2 million articles are stored in NACSIS-ELS collected by permission
from the journals and magazines published by 265 academic societies in Japan. They cover a large
proportion of academic papers written in Japanese. The average number of access to NACSIS-ELS is
now over 100 thousand for every month. It can be said that NACSIS-ELS has been grown up to be one of
the core tools for Japanese researchers when looking for scholarly information. However, there areseveral shortcomings with NACSIS-ELS. First and foremost, it does not contain any articles written in
English. A recent survey has shown that the majority of papers written by Japanese researchers are
published in foreign journals [4]. The lack of English contents certainly limits the role of NACSIS-ELS inscholarly communication. Secondly, the type of information provided by NACSIS-ELS is confined topapers. Although journal articles are the primary source of information for most researchers, theyfrequently refer to books, reports and Web pages as well. Such kind of information is entirely missing in
NACSIS-ELS.
To address these problems, we have redesigned the architecture of NACSIS-ELS in coordination withthe other information services provided by NII. The newly born NII-ELS is an enhancement ofNACSIS-ELS, which works in concert with the NII’s Citation Information Service called CiNii [5-6].
Users accessing to CiNii will subsequently be guided to the archives of papers such as NII-ELS andNII-REO (NII Repository of Electronic Journals and Online Publications) [7]. Guiding the users to otherinformation services, such as the digital libraries at foreign publishers’ sites, will also be possible if themetadata of these services are supplied to CiNii. The metadata collected from various services are mergedat CiNii into a unified database, where the identical records are linked to each other, and similar records
are grouped together. As a result, citation links from the papers in NII-ELS to the books or papers in otherservices will become active, and can be followed with a few clicks. This makes it easier to find related
information across the boundaries of services.
In this paper, we will first describe how NACSIS-ELS has been transformed to NII-ELS focusing on
the integration of the bibliographic information provided by ELS and the citation information provided byCiNii. We will then discuss the methods and framework for unifying the metadata from multiple datasources. Finally, we will outline the on-going projects aiming at linking between different types ofinformation such as papers, books, and project reports.

OVERVIEW OF NACSIS-ELSThe Electronic Library Service (NACSIS-ELS) is an information service that enables users to retrievematerials from the image databases containing photographic reproductions of academic journals andmagazines as well as from the bibliographic databases containing the secondary information of articles
and journals [1-3]. Users can search for journal articles by title, author, or keywords from the computersconnected to the Internet. They can also select articles from the tables of contents or by browsing throughpages. The images of the selected articles can be sent to the local printers to make high-quality printoutsof desired pages.
Brief History of NACSIS-ELS
The main contents of NACSIS-ELS are academic journals published by Japanese academic societies. The
amount of information available has steadily expanded as the number of participating academic societies
increases. At the time the trial service of NACSIS-ELS started in February 1995, only 3 academic
societies were providing their journals. The full-fledged service began in April 1997 with a collection ofabout 10 thousand articles, when 37 academic societies were participating in NACSIS-ELS. The numberof participating societies exceeded 100 in 1999, and the number of articles exceeded 1 million in 2001 as
shown in Fig.1.
There were several choices to make in designing the NACSIS-ELS. One was to choose between
image or full-text as the format of contents. When the conceptual design of NACSIS-ELS was being
carried out, the use of SGML, which was considered to be a probable candidate for the standard offull-text documents, was not so popular in Japan. We decided to employ images to represent the mainbody of articles, which enabled the users to view the contents in the layout of printed documents. On theother hand, the bibliographic information, such as title, author, keywords, and abstract of each article, isstored in full-text in the bibliographic databases. The combination of image and full-text data is one of theremarkable features of NACSIS-ELS.
Although the main contents of NACSIS-ELS are academic journals, it is theoretically possible to holdany type of information accompanied by an appropriate set of metadata. Examples of such information
are books collected at conventional libraries. The major obstacles in extending range of information are
the issues related to copyright protection. In the initial design of NACSIS-ELS, page images could beviewed only in special browsers or plugins exclusively developed for that purpose. Downloading theimages to local files was not permitted. That restriction was loosened a bit as Adobe’s PDF became acommon format for document delivery and was adopted by NACSIS-ELS.

Fig.1 Growth of NACSIS-ELS in terms of the number of articles and societies (As of March 2004).

Problems of NACSIS-ELSAs explained before, we have observed steady growth of contents held by NACSIS-ELS. As of June 2005,
more than 200 academic societies are participating in NACSIS-ELS. The number of articles available
exceeds 2 million. It is apparent that NACSIS-ELS now plays a substantial role in the circulation anddissemination of scholarly information in Japan.
However, the contents covered by NACSIS-ELS are limited to the articles written in Japanese. There
are no foreign publishers or academic societies participating in NACSIS-ELS. It is not likely that thesituation will change in the near future, since major foreign publishers such as Elsevier or Springer havetheir own digital libraries. The lack of English contents can be a fatal drawback of NACSIS-ELS.
According to a recent survey on the publication of scholarly papers, almost 80% of scholarly papers
written by Japanese researchers are published in foreign journals[4]. This implies that Japanese
researchers are paying more attention to foreign journals, which NACSIS-ELS does not cover.
Furthermore, for many researchers, journal articles are not the only source of information. They will
also look at books and Web pages to get necessary information. Again, such kind of information is notincluded in NACSIS-ELS.
The incomplete coverage of contents may lead to an undesirable side effect. As an advanced feature ofNACSIS, hyperlinks are embedded in the references of articles, which enable the users to follow thecitation links. The targets of these links should be articles also stored in NACSIS-ELS. As the rate ofcoverage is lowered, there will be less active links embedded in the articles. This may have a negative
influence on the behavior of users willing to collect related information.

ENHANCING NACSIS-ELS
We have already seen that the contents currently held in NACSIS-ELS are limited to journal articles
published by Japanese academic societies. Due to this limitation, NACSIS-ELS does not necessarily
satisfy the needs of Japanese researchers, who also want to access other types of information such as
articles published in foreign journals.
Overcoming the Limitation
One way to address the above problem is to import collections of metadata from other information
sources, and made them searchable in NACSIS-ELS. Nowadays, information sources such as digital
libraries typically include contents as well as metadata. Metadata are often circulated among information
providers or stored in secondary databases. By collecting and incorporating such metadata as much as
possible, we expect that NACSIS-ELS will become more convenient to use.
However, merely collecting the metadata will not always improve the situation. The format ofmetadata may differ from source to source. Therefore, it is necessary to convert the collected metadata tonormal forms, which is not easy to accomplish. Furthermore, collections of metadata obtained fromvarious sources may include duplicate records. For better usage of the entire collections, such records
should be detected and eliminated. This is a kind of “record linkage problem”, whose solution will bediscussed later.
The metadata collected from distributed sources should be converted to normal forms, and checkedfor duplicate entries. We call these processes “metadata integration.” Metadata integration is a very costly
task, sometimes requires review by human beings. As such, it should be done offline and separately fromthe service modules.
Integrating Metadata
NACSIS-ELS is not the sole service that NII is providing for academic communities in Japan. There areseveral collections whose metadata could be integrated with NACSIS-ELS. One such example is CiNii(Citation Information by NII)[5-6], which provides a gateway to the Citation Database for JapanesePapers (called CJP)[8]. Another example is NII-REO (NII Repository of Electronic Journals and Online
Publications), which holds an archive of articles of foreign journals and proceedings[7]. Currently,
Oxford University Press, Kluwer Academic Publishers1, and IEEE Computer Society are supplying theirarticles to NII-REO based on the contracts with the Japan Association of National University Libraries.
While NACSIS-ELS and NII-REO hold both the primary and secondary information, CiNii holds
only secondary information (metadata). CiNii, in its nature, is a navigator who guides the users to pieces
1

Kluwer Academic Publishers and Springer-Verlag were merged into Springer in July 2004.

hyperlinks

metadata

Integrated
metadata
collection

searchbrowsehyperlinks

metadata

Fig.2. CiNii serving as the front-end of ELS and REO.

of information they are looking for. Having examined the situation, we decided to integrate all metadata
into CiNii.
Now CiNii becomes the front-end of ELS or REO (Fig.2). Users can search information at CiNii andfollow the links from CiNii to ELS or CiNii to REO. In this framework, functions for searching andbrowsing, which were included in the original design of NACSIS-ELS, are no longer necessary. So asimplified version of NACSIS-ELS has been designed, which is called NII-ELS. NII-ELS is dedicated toarchiving articles written by researchers in Japan. We are now transferring the contents of NACSIS-ELSto NII-ELS. It will be finished by the end of March 2006, when NACSIS-ELS will cease functioning.
Detecting and Eliminating Duplicate Records
The term “record linkage” refers to the art of detecting and eliminating duplicate entries. Record linkage
becomes a crucial problem when integrating multiple databases that have been constructed independently.
It is also considered to be one of the key issues in integrating heterogeneous Web resources.
Record linkage typically consists of three stages. In the first stage, pairs of records that possibly referto the same entities are enumerated. The pairs thus enumerated are examined in detail in the second stage.
Here each pair is labeled as “match”, “possible match”, or “non-match” based on the matching score
calculated using a predefined matching function. Finally, pairs that are labeled as “possible match” areexamined by human reviewers. Details of these stages are described in [9].

Table 1. Two bibliographic records that refer to the same article.
1. TAGUCHI Isao
Observation of Nonlinear Conduction in (NbSe_4)_3I : II. LOW
TEMPERATURE PROPERTIES OF SOLIDS : Change Density
Waves
Japanese Journal of applied physics. Supplement
Vol. 26(3.pt1), pp.619-620 (1987)
2. TAGUCHI I
Observation of nonlinear conduction in (NbSe4)3I.
Jpn J Appl Phys Suppl
No.26-3 Pt.1, pp.619-620 (1987)In our experience, in integrating 1.3million bibliographic records of ELS with 0.6 million records ofCJP, we found that about 100 thousand records were redundant. Among the 100 thousand, the pairs ofrecords that were put to human review were about 5 thousand. Although these figures are largely
dependent on the nature of databases on target, it can be said that we have succeeded to construct anefficient framework for integrating bibliographic databases.

INTEGRATING HETEROGENEOUS SOURCES
The collections of metadata integrated into CiNii are not limited to those of NII-ELS and NII-REO. As ofJune 2005, Japanese Periodicals Index compiled by the National Diet Library has also been integrated.
This is one of the largest index databases extracted from the journals published in Japan, focused onacademic journals, research bulletins, and specialist magazines. More are being planned for the future,including Union Catalog Databases (serviced via Webcat Plus[10]) and Project Report Databases(serviced via KAKEN).
Incorporating Union Catalog Databases
The Union Catalog Databases (CAT) record the holdings of books and serials in university libraries andsimilar institutions. The databases have been created using the cataloging system called NACSIS-CAT,and shared by the librarians. As of March 2005, the number of libraries connected to the system is 1036,with about 80 million records. The databases can be accessed on the World Wide Web through the Webcat
Plus service.
We are planning to integrate CAT with the Citation Database for Japanese Papers (CJP). If thisintegration is completed, hyperlinks are established between references of articles records of holdings inthe catalog databases. Users can follow such links and find out which libraries hold the books referred toin a particular article.

Fig. 3. A snapshot of CiNii. By clicking the “Full Text” link of the second article, you will get the pageshown in Fig.4.

Fig. 4. A snapshot of NII-ELS.

The integration will be done based on fields of author, title, publisher, and year of publication. The
references in CJP may be in abbreviated while complete and well-formatted information is stored in CAT.
Finding identical records between CJP and CAT would be somewhat more difficult than that of CJP andELS or REO.
Incorporating Project Report Databases
The Project Report Databases serviced through KAKEN are the compiled records of projects supported
by Grant-in-Aid for Scientific Research sponsored by the Ministry of Education, Culture, Sports, Scienceand Technology (MEXT). Grants are awarded to projects organized by individual researcher or researchgroups at Japanese universities or research institutes. Each report consists of the title of the project, names
and affiliations of researchers, a summary of achievements, and a list of publications. As of June 2005,
about 300 thousand reports are held in the databases.
We view that KAKEN is useful for identifying researchers or research groups. Using such information,
articles published by the same authors can be grouped together, which will help the users of CiNii to findrelated information.
The key to this attempt is a reliable method for matching the publication lists in KAKEN databases tothe integrated collections of metadata of CiNii. Since the publication lists in KAKEN databases are notwell-formatted, we anticipate that the quality of computer-automated matching is not so high.

CONCLUSIONSNational Institute of Informatics has been providing various services to academic communities in Japan.
These include electronic library service (ELS), union catalog service (Webcat Plus), repository ofelectronic journals and online publications (REO), and citation information service (CiNii). Recently,
redesigning or modification of these services has been carried out so that they will work in concert. In
particular, NACSIS-ELS has been simplified NII-ELS, and collections of metadata in ELS has been
integrated into CiNii. We have described the background and outcome of this simplification andintegration.

We will continue to integrate more and more collections of metadata into CiNii. Some of the on-goingprojects have also been outlined aiming at integrating CiNii and CAT or KAKEN.

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